Fuel injection valve

ABSTRACT

A fuel injector ( 1 ), especially a fuel injector for fuel injection systems in internal combustion engines, has a valve needle ( 3 ) whose valve-closure member ( 4 ) cooperates with a valve seat surface ( 6 ) to form a sealing seat, and has an armature ( 20 ) engaging with the valve needle ( 3 ), the armature ( 20 ) being arranged on the valve needle ( 2 ) in an axially movable manner and being damped by a damping element ( 32 ) including an elastomer. A ring space ( 37 ) is formed between damping element ( 32 ) and valve needle ( 3 ) which is filled with fuel, ring space ( 37 ) being in contact with a throttle gap ( 39 ).

BACKGROUND INFORMATION

[0001] The present invention is based on a fuel injector of the type set forth in the main claim.

[0002] A fuel injector is known from U.S. Pat. No. 4,766,405 having a valve-closure member, connected to a valve needle, which acts together with a valve seat surface formed on a valve seat element to form a sealing seat. A magnetic coil is provided for electromagnetically actuating the fuel injector, the magnetic coil acting together with an armature which is connected to the valve needle by force-locking. Around the armature and the valve needle an additional cylindrical mass is provided which is connected to the armature via an elastomeric layer.

[0003] The disadvantage with this is particularly the costly construction method with an additional component. In addition, the large surface elastomer ring is unfavorable for the pattern of the magnetic field and hinders the closing of the field lines, and thus the achievement of great attractive forces during the opening movement of the fuel injector.

[0004] A specific embodiment of a fuel injector is also known from the above document in which, for damping and debouncing, a further cylindrical mass is provided around the armature and the valve needle, which is hemmed in and held in its position by two elastomeric rings. When the valve needle strikes the valve seat, this second mass can move relatively to the armature and the valve needle and prevent bouncing of the valve needle.

[0005] The disadvantage of this specific embodiment is the additional cost and requirement for space. Also, the armature is not decoupled, whereby its impulse on the valve needle increases the tendency to bouncing.

[0006] From U.S. Pat. No. 5,299,776 a fuel injector having a valve needle and an armature is known, where the armature is movably guided on the valve needle, and whose movement in the lift direction of the valve needle is limited by a first stop and, opposite to the lift direction, by a second stop. The play in the movement of the armature in the axial direction, fixed by the two stops, leads within certain limits to a decoupling of the inert mass of the valve needle on the one hand, and the inert mass of the armature on the other hand. Within certain limits, this counteracts the bouncing back of the valve needle from the valve seat surface when the fuel injector is closed. However, since the axial position of the armature with respect to the valve needle is totally undefined, because of the free movement of the armature, bounces are avoided to only a limited extent. In particular, with regard to the method of construction of the fuel injector known from the above document, what is not avoided is that the armature strikes the stop facing the valve-closure member during a closing movement of the fuel injector and transfers its linear momentum to the valve needle. This impact-like transfer of linear momentum may cause additional bounces of the valve-closure member.

[0007] Furthermore, it is known in practice that one may fasten the armature guided on the valve needle by an elastomeric ring in a position in which it is movably clamped. To do this, the armature is held between two flanges welded to the valve needle, there being an elastomeric ring between the armature and the lower flange. With this arrangement, however, the problem arises that a borehole through the armature is necessary for the supply of fuel to the sealing seat. The boring through the armature is made close to the valve needle, the opening of the boring facing the valve seat being partially covered by the elastomeric ring. Thereby a nonuniform compression of the elastomeric ring arises, and the bore edges finally lead to the destruction of the elastomeric ring by the pressure of the edges. Besides that, it may lead to excitation of vibrations on the part of the unsupported elastomeric ring, which also contributes to the trouble caused by the bore edges. This takes place especially at low temperatures, when the elastomer goes over into a stiff condition.

SUMMARY OF THE INVENTION

[0008] By contrast, the fuel injector according to the present invention, having the characterizing features of the main claim, has the advantage that the armature and the valve needle are damped by a fluid damper which is formed between the armature and the valve needle by the collaboration of an elastomeric ring and a fluid-filled chamber. Thereby, on the one hand, armature bounces from the lower armature stop and, on the other hand, valve needle bounces from the sealing seat are effectively damped.

[0009] Advantageous further developments of the fuel injector specified in the main claim are rendered possible by the measures given in the dependent claims.

[0010] Of particular advantage is the damping action of the damping space between valve needle and armature wall into which fuel is squeezed from the annular space during the closing movement.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Exemplary embodiments of the invention are explained in greater detail in the following description and are shown simplified in the drawings. The figures show:

[0012]FIG. 1 shows a schematic section through an example of a fuel injector having armature debouncing according to the related art,

[0013]FIG. 2 an enlarged view of a first exemplary embodiment of the fuel injector according to the present invention in region II of FIG. 1,

[0014]FIG. 3 a view of a second exemplary embodiment of the fuel injector according to the present invention in the same region as in FIG. 2, and

[0015]FIG. 4 a view of a third exemplary embodiment of the fuel injector according to the present invention in the same region as in FIGS. 2 and 3.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0016] Before exemplary embodiments of a fuel injector 1 according to the present invention are described more precisely with reference to FIGS. 2 through 4, to better understand the invention, a structurally similar fuel injector, apart from the measures according to the present invention, as it exists in the related art, shall first of all be briefly explained with respect to its important components with the aid of FIG. 1.

[0017] Fuel injector 1 is designed in the form of an injector for fuel-injection systems of mixture-compressing internal combustion engines with externally supplied ignition. Fuel injector 1 is particularly suitable for directly injecting fuel into a combustion chamber (not illustrated) of an internal combustion engine.

[0018] Fuel injector 1 includes a nozzle body 2, in which a valve needle 3 is positioned. Valve needle 3 is connected in operative connection to a valve-closure member 4 that cooperates with a valve-seat surface 6, arranged on a valve-seat member 5, to form a sealing seat. Fuel injector 1 in the exemplary embodiment is an inwardly opening fuel injector 1 which has a spray-discharge opening 7. Nozzle body 2 is sealed from external pole 9 of a magnetic coil 10 by a seal 8. Magnetic coil 10 is encapsulated in a coil housing 11 and wound on a bobbin 12 which lies adjacent to an internal pole 13 of magnetic coil 10. Internal pole 13 and external pole 9 are separated from each other by a constriction 26 and are connected to each other by a non-ferromagnetic connecting part 29. Magnetic coil 10 is energized via an electric line 19 by an electric current which can be supplied via a plug-in contact 17. Plug-in contact 17 is enclosed in a plastic jacket 18, which may be sprayed onto internal pole 13.

[0019] Valve needle 3 is guided in a valve needle guide 14, which is designed as a disk. A paired adjustment disk 15 is used to adjust the lift. An armature 20 is on the other side of adjustment disk 15. It is connected by force-locking to valve needle 3 via a first flange 21, and valve needle 3 is connected to first flange 21 by a welded seam 22. Braced against valve needle 21 is a return spring 23 which, in the present design of fuel injector 1, is prestressed by a sleeve 24. Fuel channels 30 a through 30 c run through valve needle guide 14, armature 20 and valve seat member 5, which conduct the fuel, supplied via central fuel supply 16 and filtered by a filter element 25, to spray-discharge opening 7. Fuel injector 1 is sealed by a seal 28 from a fuel line (not shown).

[0020] On the spray-discharge side of armature 20 is positioned a ring-shaped damping element 32, made of an elastomeric material. It rests on second flange 31, which is connected by force-locking to valve needle 3 via a welded seam 33.

[0021] During manufacturing of the component including armature 20 and valve needle 3, first flange 21 is welded to valve needle 3, armature 20 and damping element 32 are slipped on, and subsequently second flange 31 is pressed on damping element 32 under pressure and also welded to valve needle 3. In this way, armature 20 has only little, strongly damped play between first flange 21 and damping element 32.

[0022] In the neutral position of fuel injector 1, return spring 23 acts upon armature 20 counter to its lift direction in such a way that valve-closure member 4 is retained in sealing contact against valve seat 6. Upon excitation of magnetic coil 10, a magnetic field is generated which moves armature 20 in the lift direction, counter to the spring force of return spring 23, the lift being predefined by a working gap 27 existing in the neutral position between internal pole 13 and armature 20. Armature 20 also carries along in the lift direction flange 21, which is welded to valve needle 3. Valve-closure member 4, being connected to valve needle 3, lifts off from valve seat surface 6, and fuel guided via fuel channels 30 a through 30 c is sprayed off through spray-discharge opening 7.

[0023] When the coil current is switched off, after sufficient decay of the magnetic field, armature 20 falls away from internal pole 13 because of the pressure of return spring 23, whereupon flange 21, being connected to valve needle 3, moves in a direction counter to the lift. Thereby valve needle 3 is moved in the same direction in which valve-closing body 4 sets down upon valve seat surface 6 and fuel injector 1 is closed.

[0024] In this phase the bounces occur, which are caused on the one hand, by armature 20 falling off from internal pole 13 in the spray-discharge direction during the closing process of fuel injector 1, and on the other hand, by valve needle 3, or rather valve-closure body 4 setting down upon the sealing seat.

[0025] In an extracted sectional illustration, FIG. 2 shows the section of fuel injector 1 denoted by II in FIG. 1. Corresponding components are designated by corresponding reference numerals.

[0026] As compared to fuel injector 1 according to the related art, described in FIG. 1, the present first exemplary embodiment of a fuel injector 1 according to the present invention has an inner circular ring projection 34 on spray-discharge side 42 of armature 20, and a funnel-shaped recess 35. Fuel channel 30 a opens out on funnel-shaped recess 35. Circular ring-shaped projection 34, which is penetrated by valve needle 3 in a central recess 38 of armature 20, is supported on damping element 32, and thus on second flange 31, which is integrally connected to valve needle 3 via welding seam 33.

[0027] Second flange 31 has a ring-shaped depression 36 in which damping element 32 is arranged, and which is covered, as if by a lid, by circular ring-shaped projection 34. In this context, circular ring-shaped projection 34 lies on damping element 32. Ring-shaped depression 36 has an inner edge 43 facing valve needle 3, and a radially outer edge 44 which is axially higher than inner edge 43. Thereby circular ring-shaped projection 34 closes off ring-shaped depression 36 toward the outside, while in the neutral position of fuel injector 1 an axial gap remains between edge 43 and projection 34. In ring-shaped depression 36 an annular space 37 is formed which is radially limited by valve needle 3 and damping element 32. Annular space 37 is filled with fuel which flows into annular space 37 via central recess 38 of armature 20, which acts as a throttle.

[0028] During closing of fuel injector 1, as soon as valve-closure member sets down upon valve seat surface 6, armature 20, which is positioned movably on valve needle 3, swings through. Usually this swinging through leads to a renewed motion of armature 20 in the lift direction, which may bring on a brief, undesired further opening procedure of fuel injector 1, since thereby valve needle 3 is also moved once more in the lift direction. This is prevented in two ways by the fuel contained in ring space 37, as well as by damping element 32.

[0029] On the one hand, the fuel in ring space 37 is compressed by the at first countercurrent motions of armature 20 and valve needle 3. Armature 20 can swing through only to the point at which gap 45, between edge 43 and projection 34 of armature 20, is closed. Because of the closed form of ring space 37, the fuel can leave ring space 37 only through throttle gap 39, acting like a throttle between an inner wall 40 of armature 20 and valve needle 3. Thereby, on the one hand, the motion of armature 20, and on the other hand the swing-back motion of valve needle 3 are damped. On the other hand, in particular, the swing-back motion of armature 20 is effectively damped by damping element 32, which is positioned in ring-shaped depression 36, since damping element 32 converts a major portion of the energy of motion of armature 20 into energy of deformation of damping element 32, and because an underpressure is created in ring space 37 during the swing-back motion.

[0030] In the same view as in FIG. 2, FIG. 3 shows a second exemplary embodiment of fuel injector 1 according to the present invention.

[0031] In this exemplary embodiment, second flange 31 is furnished with a deeper ring-shaped depression 36 than in the previous exemplary embodiment. Outer edge 44 of second flange 31 is raised, while inner edge 43 is omitted. A lower end 46 of projection 34 of armature 20 is in this case formed in such a way that damping element 32 is arranged radially between thin end 46 of projection 34 and edge 44 of second flange 31, an axial gap 45 being formed between lower end 46 of projection 34 and the second flange. At equal outer diameter of second flange 31 to what it was in FIG. 2, the effective damping volume, which in this case is arranged below damping element 32, is thereby increased.

[0032] In particular, in the case of the second exemplary embodiment of fuel injector 1 according to the present invention, it is not so important to have accurately fitting and exact manufacturing or assembly of the individual components, whereby manufacturing and assembly of the component parts may be made more cost-effective.

[0033] In the mode of operation, the second exemplary embodiment of fuel injector 1 according to the present invention is similar to the first exemplary embodiment shown in FIG. 2. When the fuel injector 1 is closed, armature 20 swings through, whereby damping element 32 as well as the fuel in ring space 37 are compressed by projection 34 of armature 20. Armature 20 can only swing through until lower end 46 of projection 34 strikes second flange 31. Damping element 32 absorbs the greatest part of the energy of motion of armature 20, while the fuel displaced from ring space 37 flows out via throttle gap 39 between valve needle 3 and inner wall 40 of armature 20, whereby the swinging through of valve needle 3 is braked and valve-closing member 4 is prevented from once again briefly lifting off from valve seat surface 6.

[0034] The third exemplary embodiment of fuel injector 1 according to the present invention, shown in FIG. 4, differs little in its construction from the two previous exemplary embodiments. Instead of circular ring-shaped projection 34 of armature 20, a cap-shaped cover shell 41, on which projection 34 of armature 20 is supported, forms the ring-shaped depression 36. In the third exemplary embodiment, ring-shaped depression 36 opens in the downstream direction of the fuel flow. Second flange 31 is designed to be flat here and closes ring-shaped depression 36 like a lid in the downstream direction. Cover shell 41 has the special advantage that it is particularly easy to manufacture as a separate part, independently of armature 20.

[0035] Damping element 32 is positioned in ring-shaped depression 36 of cover shell 41, and ring space 37 is in contact with throttle gap 39, as in the preceding exemplary embodiments, between inner wall 40 of armature 20 and valve needle 3. The component parts of the third exemplary embodiment have the advantage that, on the one hand, they are particularly easy to manufacture, and on the other hand, armature 20 may be configured in such a way that fuel channel 30 a, inserted into armature 20, may be processed more easily and deburred at its downstream end.

[0036] At the closing of fuel injector 1, armature 20 swings through again in the spray-discharge direction, whereby cap-shaped cover shell 41 is pushed over second flange 31, since the outer diameter of flange 31 is equivalent to the inner diameter of the mantle region of cover shell 41, or rather, is minimally smaller. In the present exemplary embodiment, advantageously gap 45 does not have to be limited by a special geometrical arrangement as was the case in the exemplary embodiments described above, but is, in this case, equal to the height of ring space 37. Damping element 32, lying between cover shell 41 and second flange 31, as well as the fuel present in ring space 37 are compressed by the movement, and in this context, damping element 32 absorbs the energy of motion of armature 20, while the fuel from ring space 37 is displaced into throttle gap 39 between valve needle 3 and inner wall 40 of armature 20. The swinging through of valve needle 3 is damped by the viscosity of the fuel and/or the throttle effect of throttle gap 39.

[0037] The present invention is not limited to the exemplary embodiments shown, and is also suitable, for example, for flat armatures or for any design of fuel injector. 

What is claimed is:
 1. A fuel injector (1), especially a fuel injector for fuel injection systems in internal combustion engines, having a valve needle (3) whose valve-closure member (4) cooperates with a valve seat surface (6) to form a sealing seat, and having an armature (20) engaging with the valve needle (3), the armature (20) being arranged on the valve needle (3) in an axially movable manner and being damped by a damping element (32) made of an elastomer, and arranged between a flange (31) and the armature (20), wherein a ring-shaped depression (36) is formed on the flange (31) on which the damping element (32) is arranged, and a ring space (37) is formed, between the valve needle (3) and the damping element (32), which is filled with fuel, the ring space (37) being in contact with a throttle gap (39) at the valve needle (3).
 2. The fuel injector as recited in claim 1, wherein the throttle gap (39) is formed between the valve needle (3) and an inner wall (40) of the armature (20).
 3. The fuel injector as recited in claim 1 or 2, wherein a circular ring-shaped projection (34) of the armature (20) covers the ring-shaped depression (36).
 4. The fuel injector as recited in claim 3, wherein the projection (34) of the armature (20) lies against the damping element (32) arranged in the ring-shaped depression (36).
 5. The fuel injector as recited in one of claims 1 through 4, wherein the armature (20) has a funnel-shaped recess (35) on a discharge side (42) into which a fuel channel 30 a, which penetrates the armature (20), discharges.
 6. The fuel injector as recited in one of claims 1 through 5, wherein an inner edge (43) of the flange (31) facing the valve needle (3) is lower than an outer edge (44) of the flange (31).
 7. The fuel injector as recited in claim 6, wherein between the inner edge (43) and a projection (34) of the armature (20) a gap (45) is formed.
 8. The fuel injector as recited in claim 7, wherein the gap (45) is in contact with the throttle gap (39).
 9. The fuel injector as recited in one of claims 4, 7 or 8, wherein the projection (34) has a lower end (46) whose diameter is smaller than the diameter of the flange (31).
 10. The fuel injector as recited in claim 9, wherein the damping element (32) is radially clamped between the lower end (46) of the projection (34) and the flange (31).
 11. The fuel injector as recited in one of claims 4, 7, 8, 9 or 10, wherein the projection (34) is supported on a cover shell (41), which is designed cup-shaped and penetrated by the valve needle (3).
 12. The fuel injector as recited in claim 11, wherein the flange (31) is designed disk-shaped flat and has an outer diameter equivalent to the inner diameter of the cover shell (41).
 13. The fuel injector as recited in claim 12, wherein the damping element (32) is arranged between the cover shell (41) and the flange (31). 